7aa

Author: FrancescoXX

book-compendium/chapter-7a/21_validating_references_impl.rs

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+// 21_validating_references_impl.rs
+
+// 1. The Trait Definition (Required context)
+trait Parse<'a> {
+    fn parse(input: &'a str) -> Self;
+}
+
+// 2. The Struct with References
+// We declare <'a> to tell the compiler: 
+// "address" and "port" are strictly tied to the lifetime 'a.
+#[derive(Debug)]
+struct ServerConfig<'a> {
+    address: &'a str,
+    port: &'a str,
+}
+
+// 3. The Implementation
+// This line is often tricky for beginners. We have three 'a usages:
+// 1. impl<'a>: We declare the lifetime generic for this block.
+// 2. Parse<'a>: We are implementing the version of Parse tied to 'a.
+// 3. ServerConfig<'a>: We are implementing it for the struct tied to 'a.
+impl<'a> Parse<'a> for ServerConfig<'a> {
+    fn parse(input: &'a str) -> Self {
+        // A very simple parser that splits by space.
+        // Note: split(' ') returns an iterator yielding slices of the original string.
+        // No new memory is allocated for the address or port strings!
+        let mut parts = input.split(' ');
+        
+        ServerConfig {
+            address: parts.next().unwrap_or("localhost"),
+            port: parts.next().unwrap_or("8080"),
+        }
+    }
+}
+
+fn main() {
+    // The raw configuration data (owned string)
+    let config_data = String::from("127.0.0.1 9000");
+
+    // We parse it into our struct.
+    // 'server' now borrows from 'config_data'.
+    let server = ServerConfig::parse(&config_data);
+
+    println!("Server Configuration:");
+    println!("Address: {}", server.address);
+    println!("Port:    {}", server.port);
+
+    // If we dropped 'config_data' here, we could no longer use 'server'.
+    // drop(config_data); // Uncommenting this would cause a compile error!
+}